Mech

Lol... You won't need luck.

Two screwdrivers crossed above the center of the unit, with their tips hooked in behind the lugs, and then both used to lever against the other so it turns the flange thingy. Have you ascertained it is the sender unit faulty ? When you put it back in, a smear of vaseline/petroleum jelly on the seal will make it go together real nice.

Well clean it, start it up and watch it while it's running for a few minutes. If oil starts appearing then that's your leak. If it doesn't leak go for a ten minute ride and recheck for oil leaking, if it's still no leak go for a half-hour ride. Under that oil cooling pipe flange there will be a rubber O ring I'd think, or possibly a gasket. The oil filter will have a built in rubber ring for sealing so you could try turning that about a 1/8 turn if it's not already tight. The oil filter should seal at only hand tight, sort of wind it down till the rubber seal touches then about another half to one turn. If the filter was put on without a wipe of oil on it's sealing rubber it might have bunched up and not be sealing properly. If it is the filter leaking then you could undo it until the seal comes off the mating surface and then tighten it down hand tight again.

I think I'd just live with those tyres till I'd put some hours on the bike and made sure nothing more serious was wrong.

On that type you turn a big locking ring that holds the tank unit down. The rubber seal under it should be reusable.

Figure which wire on the tank unit is the gauge wire and short it to earth. The gauge should swing. Be careful not to try shorting the pump wire ! Here's the procedure for removing the tank unit. Hisun..pdf

The oil's higher up the engine than the oil pipe, so it's possible that that oil leaked from the oil filter, or got there when the filter got changed. It doesn't really look wet either, which would suggest it's not leaking now or recently. I'd use some fuel and then the garden hose to wash it clean and then keep an eye on it, it may not leak at all, and if it does you will be able to see where it's come from if you look before it's spread the oil about.

Good plan Gw..

Has this started after the bike's been siting for a while getting the repairs done ? Is the fuel fresh ? Could moisture have condensed in the carb ? Check the plug is clean and has a good blue spark, then undo the drain screw under the carb and make sure fuel keeps coming out at a good rate. Keep flowing fuel till you are sure the carb should be empty and make sure it doesn't stop delivering plenty of fuel. Catch the fuel and check there wasn't water in it. If there was water then clean the tank and test the bike again. If it's getting plenty of fuel to and right through the carb then it's probably time to take the carb off and give it a good clean. I usually start by taking the top cover off before taking the carb off the bike, and checking the diaphragm isn't split and that the slide needle hasn't come loose, or adjusting the needle (if the circumstances seem likely that it's in need of adjustment), but if the problem just arose then just that it's not jumping up and down, or dropped down through the slide. Then I'd remove the carb and strip it entirely down and clean it and reassemble it.

It's nice and warm here in N.Z, so I'd probably go for one of those things you put on the seat behind you in a bikini..

A little leak up at the head to exhaust pipe join, or anywhere in the first few inches of pipe, will make them backfire. Tried these guys.. They have always been good exhausts at a fair price. https://www.musketmufflers.com/

A bad misfire can cause a sooty black plug, but it has to miss a lot and for a while.. I'm thinking you would notice that. If it only goes rich occasionaly, and if it was only when you throttle off hard as would be the case if the choke was stuck on, then you wouldn't particularly notice the richness.. That could also explain why the idle mixture doesn't respond to adjustment.. -

Old worn low compression engines do get a build up on their plug, but it's generally a healthy tan or grey hard build up, not sooty. Worn rings burning oil, or leaking valve stems letting oil in to be burnt, the plug goes black and oily looking .. Black soot is always rich mixture I think..

Start the bike and operate the choke.. You should be able to hear if it's working, or doing nothing. The choke only sucks fuel up when the throttle's closed. Soon as you open the throttle the vacuum drops in the choke circuit and it doesn't lift the fuel right to the top of the venturi where the discharge for the choke is. So it could be on and only go rich when you throttle off hard. It does seem unusual to have fluffy dry soot that fast. That's definitely rich though.. Oil looks wet black. You have got fresh fuel haven't you ? And a good grade ? The compression is probably meant to be nearer 175 Lb but that's warm and with a full open throttle and cranking at the right speed. If it comes up to it's 125 in the first couple of compression strokes it's a good sign. If it has to be cranked a lot and slowly creeps up with each compression stroke it's a bad sign. You could put a teaspoon of oil down the plug hole, give it a quick spin with the starter or pull start to distribute the oil, then do a compression check. If the oil raises the compression a lot it points to rings, not valves. Having a tight or leaking valve doesn't normally cause dry fluffy sooty spark plug. Leaking rings doesn't normally cause that sort of soot either.. Only fuel does that. Some bikes say what size the jets are in the parts manuals. You can look that up online, or in a service manual.

Sounds like the charging isn't working. Check the fuses and the connection between the regulator and the battery, both power and earth connections, then the next check is that the stator is putting AC power out down at the engine, or even better, that the AC is getting to the regulator.

#41 I'm not sure which sensor is fitted where on the bike. I only know one has one wire and one has two. If putting power into the fan makes the fan run then the fan is ok. My test procedure is testing which place along the wiring system the disconnect is that's preventing it from going. The most common sign of a blown head gasket is bubbles coming up in the radiator. Steam could be caused by the air being very cold ? Warm water always looks like it's steaming if the air over it is cold enough. Even a farm pond can look like steam's rising up off it. If the engine is really overheating in fifteen minutes of idling it could be the thermostat, the water pump, the head-gasket, a blocked or dirty radiator.

Have you looked at that wiring diagram I posted for you at #32? There are two temp sensor switches, one has one wire and the other has two. They use different coloured wires. If you follow the recommendations/test procedure in #34 it should find the fault with the fan, if there is a fault with the fan. Most engines won't overheat in fifteen minutes of idling from cold. It may be that you have a blown head-gasket, faulty water pump, blocked radiator, or a radiator that's dirty on the outside. If you take the radiator cap off and let it idle with a full to the brim radiator, there shouldn't be any bubbles coming up in the filler. I'd check that.

Dry black soot sure sounds like too much fuel. The mixture adjustment doing nothing is always a sign of something wrong in a carb. Since it's running good, no mention of missing or hard start etc I'd doubt the ignition is at fault. Check it's got a reasonably fat blue spark. Ignition systems with resistor caps or leads can have a skinny spark, but it should be blue. If it looks yellow it's a bad sign. If the soot is only on the porcelain tip it might pay to try a hotter plug. If it lost it's spark suddenly it might have a wet plug, but it wouldn't have black soot. I'd make sure the fuel tap was good and not filling the sump with fuel. And if it's got a vacuum controlled tap check that isn't letting fuel into the vacuum line. Then I'd start looking at the mixture. Choke's going right off, check that first because the choke only works when the throttle's shut so they run ok with a stuck on choke, till you throttle off, then air-filter, intake piping isn't crushed or blocked(mouse nest), carb breather tubes, fuel tank breather. It might be that the richness is intermittent, or caused by heat or the time run. So check the carb breathers, and tank's not presurising. Then It'd be off with the carb for another look. Check the float height(can be done before pulling the carb off) and that it isn't sinking, check the idle mixture screw tip and the seat the screw goes into for damage, check the float needle seat is sealed to the body, the breather drillings are clear, all the drillings are clear, the jets are the right size, the slide needle is the right one and attached to the slide, the slide isn't sticking. Reassemble and check the idle mixture is responsive. If it isn't then there's still something wrong in the carb.

Probably on the outer side of the lower frame member just in front of the front of the gear shift lever.

There are two temperature sensing switches. One is wired back to the dash with a violet wire, and the other one has two red wires. The switch you are looking at is in the lower left of that wiring diagram I posted. The power for the fan comes from a fuse to the temperature sensing switch connector in a black wire with a red stripe (blk/red), Then the switch's wires are both red, and one of them comes back out of the switch and goes to the fan motor when the switch closes. It goes through the fan motor and comes back out on a black wire as far as the fan's connector where it turns into a black wire with a white stripe as far as the diode, and after the diode it's a black wire connected to earth. And yes, the diode has to conduct to earth for the fan to operate.

Yes, a lot of people do add a bit of oil with the fuel as an extra safety measure, and a having a two-stroke running with a bit of extra oil going through it does seem to make them last longer.

Diagram up further. The diode's between the fan and earth.

Is this backfire making a load popping or banging sound, or is it just blowing fuel fumes back out the carb ? And, is the bike idling ok with this backfiring ? If you give it throttle what happens ? Does it come right or get worse ?

If the diode was open circuit it would stop the fan coming on. Check power is getting to the temp switch with a test light, not a gauge, then unplug the switch and bridge across the plug on the bikes wiring with a wire. That should make the fan go. If the fan doesn't go then, check there is power getting to the fan's red wire using a test light. If there is power to the fan, bridge across the diode with a piece of wire and see if the fan goes. To bridge the diode you can just put a wire from black wire of the fan straight to a good earth.

It's a two-stroke engine but you don't need to premix oil in the fuel. It has an oil tank and it auto mixes the oil as it runs. You need to top the oil tank up every so often. I think the oil tank will last longer than a tank of gas for safety reasons, but you need to monitor it for a while to be sure about that. It may not last two tanks of gas ! There should be a manual for it in the manuals section..